ubuntu server 官方的源代码更新比较慢，所以更替成国内的源。
操作如下：
piaoyun@Ubuntu:~$ sudo cp /etc/apt/sources.list /etc/apt/sources.list.apt
piaoyun@Ubuntu:~$ sudo vim /etc/apt/sources.list
或者使用nano编辑：
piaoyun@Ubuntu:~$ sudo nano /etc/apt/sources.list
ctrl+o   #保存配置
ctrl+x   #退出编辑

#更替163源或者sohu源
piaoyun@Ubuntu:~$ sudo apt-get update

中国科学技术大学源：

Trusty(14.04)

deb http://mirrors.ustc.edu.cn/ubuntu/ trusty main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ trusty-security main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ trusty-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ trusty main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ trusty-backports main restricted universe multiverse

Quantal(12.10)

deb http://mirrors.ustc.edu.cn/ubuntu/ quantal main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ quantal-security main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ quantal-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ quantal-proposed main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ quantal-backports main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ quantal main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ quantal-security main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ quantal-updates main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ quantal-proposed main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ quantal-backports main restricted universe multiverse

Precise(12.04)

deb http://mirrors.ustc.edu.cn/ubuntu/ precise main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ precise-security main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ precise-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ precise-proposed main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ precise-backports main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ precise main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ precise-security main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ precise-updates main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ precise-proposed main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ precise-backports main restricted universe multiverse

Oneiric(11.10)

deb http://mirrors.ustc.edu.cn/ubuntu/ oneiric main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ oneiric-security main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ oneiric-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ oneiric-proposed main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ oneiric-backports main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ oneiric main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ oneiric-security main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ oneiric-updates main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ oneiric-proposed main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ oneiric-backports main restricted universe multiverse

Natty(11.04)

deb http://mirrors.ustc.edu.cn/ubuntu/ natty main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ natty-security main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ natty-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ natty-proposed main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ natty-backports main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ natty main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ natty-security main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ natty-updates main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ natty-proposed main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ natty-backports main restricted universe multiverse

阿里云源：

Trusty(14.04)

deb http://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse

Quantal(12.10)

deb http://mirrors.aliyun.com/ubuntu/ quantal main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ quantal-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ quantal-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ quantal-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ quantal-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ quantal main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ quantal-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ quantal-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ quantal-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ quantal-backports main restricted universe multiverse

Precise(12.04)

deb http://mirrors.aliyun.com/ubuntu/ precise main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ precise-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ precise-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ precise-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ precise-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ precise main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ precise-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ precise-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ precise-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ precise-backports main restricted universe multiverse

Oneiric(11.10)

deb http://mirrors.aliyun.com/ubuntu/ oneiric main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ oneiric-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ oneiric-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ oneiric-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ oneiric-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ oneiric main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ oneiric-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ oneiric-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ oneiric-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ oneiric-backports main restricted universe multiverse

Natty(11.04)

deb http://mirrors.aliyun.com/ubuntu/ natty main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ natty-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ natty-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ natty-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ natty-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ natty main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ natty-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ natty-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ natty-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ natty-backports main restricted universe multiverse

163源：

Trusty(14.04)

deb http://mirrors.163.com/ubuntu/ trusty main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ trusty-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ trusty-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty-backports main restricted universe multiverse

Quantal(12.10)

deb http://mirrors.163.com/ubuntu/ quantal main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ quantal-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ quantal-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ quantal-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ quantal-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ quantal main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ quantal-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ quantal-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ quantal-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ quantal-backports main restricted universe multiverse

Precise(12.04)

deb http://mirrors.163.com/ubuntu/ precise main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ precise-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ precise-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ precise-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ precise main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ precise-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ precise-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ precise-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse

Oneiric(11.10)

deb http://mirrors.163.com/ubuntu/ oneiric main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ oneiric-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ oneiric-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ oneiric-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ oneiric-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ oneiric main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ oneiric-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ oneiric-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ oneiric-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ oneiric-backports main restricted universe multiverse

Natty(11.04)

deb http://mirrors.163.com/ubuntu/ natty main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ natty-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ natty-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ natty-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ natty-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ natty main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ natty-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ natty-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ natty-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ natty-backports main restricted universe multiverse

sohu源：

Trusty(14.04)

deb http://mirrors.sohu.com/ubuntu/ trusty main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ trusty-security main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty-backports main restricted universe multiverse

Quantal(12.10)

deb http://mirrors.sohu.com/ubuntu/ quantal main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ quantal-security main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ quantal-updates main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ quantal-proposed main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ quantal-backports main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ quantal main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ quantal-security main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ quantal-updates main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ quantal-proposed main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ quantal-backports main restricted universe multiverse

Precise(12.04)

deb http://mirrors.sohu.com/ubuntu/ precise main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ precise-security main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ precise-updates main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ precise-proposed main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ precise-backports main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ precise main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ precise-security main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ precise-updates main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ precise-proposed main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ precise-backports main restricted universe multiverse

Oneiric(11.10)

deb http://mirrors.sohu.com/ubuntu/ oneiric main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ oneiric-security main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ oneiric-updates main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ oneiric-proposed main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ oneiric-backports main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ oneiric main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ oneiric-security main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ oneiric-updates main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ oneiric-proposed main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ oneiric-backports main restricted universe multiverse

Natty(11.04)

deb http://mirrors.sohu.com/ubuntu/ natty main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ natty-security main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ natty-updates main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ natty-proposed main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ natty-backports main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ natty main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ natty-security main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ natty-updates main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ natty-proposed main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ natty-backports main restricted universe multiverse

apt使用
apt-get update #更新索引
apt-cache search nginx  #搜索关键字还有nginx的包
apt-get install nginx #安装nginx

然后会出现key无法找到。然后执行：
piaoyun@Ubuntu:~$ sudo apt-key adv –keyserver keyserver.ubuntu.com –recv-keys < add keys here >
piaoyun@Ubuntu:~$ sudo apt-get update

解决ubuntu server 12.04更换源后gpg错误的解决办法。
更换了一个更快的源，使用sudo apt-get update报了一个gig错误：
W: GPG error: http://extras.ubuntu.com precise Release: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 16126D3A3E5C1192

使用google查询到解决办法：
$gpg –keyserver keyserver.ubuntu.com –recv 3E5C1192
$gpg –export –armor 3E5C1192 | sudo apt-key add -
$sudo apt-get update

若执行apt-get update产生错误
【错误现象】
E: Could not get lock /var/lib/apt/lists/lock – open (11 Resource temporarily unavailable)
E: Unable to lock the list directory
【错误原因】可能为之前操作使用ctrl+c强制退出apt-get 指令，而实际apt-get进程依然存在。

【解决方法】
查看进程(使用grep指令过滤其他进程)
ps -e | grep apt

apt-get进程依然存在
6362 ? 00:00:00 apt
6934 ? 00:00:00 apt-get

销毁进程
sudo killall apt
sudo killall apt-get

重新执行
sudo apt-get update